1. Technical Field
Various embodiments generally relate to image sensors and, more particularly, to image sensors configured by complementary metal oxide semiconductors (CMOS) and fabricating methods thereof.
2. Related Art
Image sensors sense external images as light, convert sensed light into electric signals, and transmit the electric signals to devices that process digital signals. Generally, there are two kinds of image sensors, charge-coupled device (CCD) image sensors and complementary metal oxide semiconductor (CMOS) image sensors.
CCD image sensors include photodiodes that are formed on P type impurity layers, CCDs, and signal detection circuits. The photodiodes convert light into charges. The CCDs transmit the charges to the signal detection circuit, and the signal detection circuit converts the charges into voltages and then outputs the voltages.
The CMOS type image sensor includes CMOS transistors in which a PMOS (P-channel metal oxide semiconductor) transistor and an NMOS (N-channel metal oxide semiconductor) are joined, and converts images into electric signals. Since the CMOS technology is capable of being highly integrated and operating with low power consumption, CMOS technology is often used in small-sized electronic appliances, such as mobile phones.
CMOS image sensors include active pixel arrays, which receive light, and optical black pixel arrays, which block light.
The active pixel arrays have pixels that receive light, resulting in the generation and accumulation of photo charges. The optical black pixel array blocks the introduction of unwanted light to minimize interference. As the active pixel array and the optical black pixel array have different functions, they also have different structures.
Japanese Patent Publication No. 2011-114292 discloses an active pixel array and an optical black pixel array that have different structures and are fabricated by different processes. Thus, that image sensor fabrication process is complicated and expensive. The invention disclosed herein seeks to simplify the image sensor fabrication process and improve image sensor product quality.